Patrick Hennessy writes about politics for the Telegraph.

Why aren't the Tories steaming ahead?

Much debate in Tory circles and the blogosphere (the two are often exactly the same thing) about why, given the government's current travails, the Conservatives are not doing better in the opinion polls. David Cameron's party appears to be becalmed, if that is the right word, at 40 per cent or just over.

Cameron's party is becalmed, despite Labour's woes

Not a bad place to be – but still some way short of the mid-to-high forties achieved consistently by Labour in the mid 1990s as John Major's government was falling apart. The reasons for this are said to be, variously, a continuing lack of direction over policy, a concentration on tactics (party funding for example) rather than strategy, and Mr Cameron's resemblance to a public school bully as he beats up the beleaguered PM.

I believe there is another – simpler – reason: the ditching of Sir Menzies Campbell by the Liberal Democrats in October. Since then the Lib Dems have been in the news thanks to their leadership election, which always sends a party's poll rating up, if only temporarily.

As Conservative Home's excellent opinion poll tracker shows the defenestration of the hapless Ming has helped the Lib Dems recover from the depths of the 11 or 12 per cent they had been recording under him to a solid rating in the high teens. One survey even put them on 21 per cent. It is a fair bet that this rise has been largely at the expense of the Tories.

If Nick Clegg becomes leader (which still looks likely though by no means certain) expect a battle royal for Tory votes all the way up to the next election as he looks to build on this success.